1. Field of the Invention
The present invention relates to a percussion driver drill capable of effecting a changeover among a plurality of operating modes thereof. Furthermore, the present invention also relates to a changeover mechanism for changing over a plurality of operating modes of an apparatus such as a power tool, a motor-driven device, an electric equipment, etc.
The present application is based on Japanese Patent Applications Nos. Hei. 11-35880 and Hei. 11-35922, which are incorporated herein by reference.
2. Description of the Related Art
A percussion driver drill is known as one of power tools. As the structure for changing over the operating mode of a percussion driver drill, a structure is known in which, as disclosed in Unexamined Japanese Patent Publication No. Hei. 6-339868, a cam mechanism, which is comprised of a rotating ratchet secured on a spindle and provided with ratchet teeth in an axial direction as well as a fixed ratchet fitted loosely over the spindle and having similar ratchet teeth formed on its surface opposing the rotating ratchet so as to be prevented from rotating, is controlled by a first changeover member such as a ring member or a lever. Namely, in a first changeover position of the first changeover member, the fixed ratchet moves toward the rotating ratchet side to cause their ratchet teeth to interfere with each other, whereby, in addition to rotation, axially percussing motion is applied to the spindle (percussion mode). Meanwhile, in a second changeover position, the fixed ratchet moves away from the rotating ratchet, so that only rotation is applied to the spindle (drill mode).
In addition, in the aforementioned publication, a torque adjusting mechanism is also adopted in which, in a planetary gear reduction mechanism disposed in a stage preceding the spindle, one of internal gears meshing with a periphery of a planetary gear is made rotatable inside a housing, and this internal gear is pressed and fixed by a pressing mechanism including steel balls, washers, and a coil spring, wherein if the load on the spindle increases, the internal gear is caused to idle to cut off the transmission of rotation of the spindle. The setting of the torque is possible by changing the pressing force of the coil spring by rotatively operating a second changeover member such as a ring member meshing with the housing and supporting a front end of the coil spring.
Meanwhile, also disclosed in the aforementioned publication is an arrangement in which the changeover of the cam mechanism and the changing of the pressing force of the coil spring are made possible by a single changeover member.
When the percussion driver drill is to be used in the percussion mode and the drill mode, in addition to the operation of changing over the operating mode by the first changeover member, the operation of the second changeover member is required in order to maximize the torque so that the internal gear does not idle easily due to the load. To the contrary, when the percussion driver drill is to be used for screwdriving or the like from the percussion or drill mode, in addition to the changeover operation to the drill mode by the first changeover member, it is necessary to operate the second changeover member again to a desired torque from the maximum torque so that torque adjustment functions. Thus, when the percussion driver drill is used selectively between the percussion or drill mode and the torque adjustment, the operation of the two changeover members is always required, so that the handling of the percussion driver drill has been troublesome, and the ease of its use has been poor.
On the other hand, also in a case where both the changeover of the operating mode and the torque adjustment are effected by one changeover member, in the alternate use for drilling and screwdriving, there are cases where the percussion driver drill is used by alternately rotating the changeover member (here, a change ring) by maximum amounts clockwise and counterclockwise, so that the ease of its use has been poor.
In addition, with the percussion driver drill, there are cases where the changeover of the operating mode among such as the percussion mode and the drill mode as well as the torque adjustment are respectively effected by using separate changeover members. For example, in Registered Japanese Utility Model No. 3004054, a percussion driver drill is disclosed in FIGS. 8 and 9 in which a dial-type first changeover member for changing over the operating mode between the percussion mode and the drill mode and a dial-type second changeover member for adjusting the torque of the spindle are disposed at forward and backward positions in the axial direction in front of the housing, and as each of these changeover members is rotatively operated, selection of the operating mode or torque is made possible.
In the percussion driver drill thus provided with the changeover members, clicking mechanisms using such as a leaf spring and balls are provided to improve the operational efficiency by providing positioning in predetermined rotational positions. However, the two changeover members are often spaced apart from each other so as to indicate marks for the rotated positions between the two changeover members, or the clicking mechanisms are often disposed separately on the front and rear sides of the two changeover members partly because the number of clicking pieces differs between the first changeover member and the second changeover member (in the aforementioned publication, two clicking pieces are provided in the first changeover member, and six clicking pieces are provided in the second changeover member). Consequently, there have been problems in that the structure becomes complex and the cost becomes high, and that the space for the clicking mechanisms becomes large, making the percussion driver drill elongated in the axial direction.